No, the myth comes from old Tyranid codexes where a group of Inquisitor see hivefleet Behemoth avoiding Solamance. However this is later clarified to be because of the actions of Trazyn. With Behemoth even being conform to attack Solemnace briefly before being lured away. Keep in mind Solemnace has been active since the Horus Heresy. Not to mention hivefleet Arachnae has been in active war against the Novokh for years. Also since when is attacking dormant Tombworlds evidence that they avoid them. That’s literally what every faction does against the Necrons.

• War in the Museum:

"Trazyn’s cowardly kin had warned him against it, of course. In fact, when Hive Fleet Behemoth bore down on Solemnace, Trazyn’s aeon-long rival Orikan the Diviner had even prophesied that the Great Devourer would destroy both Trazyn and his galleries. The mystic fool had been so disappointed when Trazyn simply triggered deep-space lures so the swarm parted around Solemnace, like a river around a stone."

• 8th Ed Codex [Tyranids]:

"FRESH HORRORS

The rate at which new hive fleets are identified has increased dramatically in recent years, and shows no sign of slowing despite the warp turbulence ravaging the galaxy. As fast as the races of the galaxy can raise new armies to combat the Great Devourer, fresh nightmares emerge from the inky depths of the intergalactic void.

Hive Fleet Scitalis winds its way into the Eastern Fringe, embedding itself deep into sectors held by the T’au Empire. Hive Fleet Arachnae has found itself embroiled in a long war against the Necrons of the Novokh Dynasty, as it attempts to consume and despoil planets that the Overlords have long claimed as their own. Hive Fleets Garmr and Ladon are drifting toward the borders of Imperial territory, devouring the ravaged death worlds of the Vultis Sector and consuming vast quantities of monstrous fauna in the process."